This invention relates to an internal combustion engine and more particularly to a variable valve timing arrangement for such engines and more specifically to a control valve arrangement for controlling the variable valve timing.
As is well known, many facets of engine design represent a compromise between obtaining high maximum power output and good running under low speed low load conditions. One of the factors that affect this performance is the valve timing of the engine.
The use of variable valve timing mechanisms facilitates the ability of the engine to run over a wider range of speeds and loads with optimum performance under each running condition.
Generally, variable valve timing mechanisms employ a hydraulic actuator that adjusts the phase angle between the driving element of the cam shaft and the cam shaft so as to change the valve timing relative to the crankshaft angle. These variable valve timing mechanisms can be used with either or both of the intake and/or exhaust cam shafts.
In order to provide the hydraulic force for actuating the variable valve timing mechanism, it has been the practice to employ the lubricant from the lubricating system of the engine. This lubricant is selectively applied to the variable valve timing mechanism by a control valve so as to accomplish the phase angle adjustment.
It has generally been the practice to mount the variable valve timing mechanism at the outboard end of the cam shaft and adjacent its forwardmost bearing. In order to cut down fluid losses and minimize the effects of leakage, it has been the practice to introduce the oil for the valve timing mechanism to the cam shaft through this forwardmost bearing surface. The control valve is then mounted in proximity to the bearing surface so as to control the application of the hydraulic pressure.
With these types of arrangements, it has been the practice to have the supply and discharge passages intersect the forwardmost bearing surface of the cam shaft and also to have the control valve mounted in proximity to the bearing surfaces. As a result, it has been necessary to employ a modified fastening arrangement for holding the forwardmost bearing cap in position. This presents some problems.
Specifically, it is desirable if the bearing cap is fastened to the engine body in axial alignment with the portion of the bearing surface in which the control valve communication ports are formed. However, this is the area where the variable valve timing control valve is normally positioned with most conventional applications. As a result, it is the practice to move the fasteners for the bearing cap to a location that is axially spaced from the bearing surface. This does not provide uniform loading nor good sealing.
It is, therefore, a principal object of this invention to provide an improved control valve and bearing arrangement for the variable valve timing arrangement of an internal combustion engine.
It is a further object of this invention to provide a bearing and valve arrangement for an engine wherein the number of bearing cap fasteners can be reduced and those fasteners juxtaposed to the associated bearing surfaces to improve sealing and hold down conditions.